1. Field of the Invention
The present invention relates to a novel fluid-permeable article or product and a method for producing such an article, and more particularly to a method suitable for producing a novel cast product having continuous pores which permit a fluid to pass therethrough, without any metallurgical or mechanical treatment.
2. Discussion of the Prior Art
Various cast articles of iron, steel, copper alloy, aluminum alloy or other material are widely used for machine tools and general industrial machine equipment and for other applications. Such cast articles are produced by pouring a suitable molten metal into a cavity formed in a casting mold, and solidifying the cast metal melt.
The metal product thus produced by molding are subjected to post-casting treatments such as machining, grinding, lining, heat treatment, mechanical or chemical treatments, and various other treatments, depending upon the applications of the metal castings, in order to improve the properties of the products as cast.
In the field of metal casting as indicated above, it is known to use a core placed within a casting mold, for producing a hollow article which has a cylindrical hole corresponding to the core, for example. While it is possible to cast such a hollow article by using a core, no methods have been proposed for providing the hollow article with a three-dimensional porous structure which has continuous capillary pores as formed in a sintered metal article, and which permits a fluid to pass therethrough. Further, it is recognized that such continuous capillary pores are very difficult to form by any post-casting machining operations.
Thus, it has been extremely difficult to cast a porous structure having a continuous network of capillary pores, which may be used as an oil-impregnated bearing or ring for textile machinery, for example, wherein a lubricant is accommodated within the continuous network of the capillary pores in the porous structure. On the other hand, a cast iron base for a machine tool is required to have an air-permeable porous structure, when the machine base is designed as a pneumatically hovering or levitating member. In this case, the cast machine base must be subjected to a number of time-consuming and difficult drilling operations to form therein a multiplicity of mutually communicating small holes.